Conventionally, there has been proposed a drain recovery system that supplies steam generated at a boiler to a load device, and that recovers drain generated from the steam having used as a heat source at the load device, to reuse the drain as feedwater to the boiler.
As the drain recovery system, there has been known an open scheme drain recovery system that recovers drain generated at a load device to an open type drain recovery tank opened to the atmosphere and that supplies the drain to a boiler, and a closed scheme drain recovery system that recovers drain of high temperature and high pressure to a pressure-resistant sealing drain recovery tank and that supplies the drain as feedwater to a boiler (for example, see Patent Literature 1).